Crystal Facet Engineering of TiO2 Nanostructures for Enhancing Photoelectrochemical Water Splitting with BiVO4 Nanodots
Mi Gyoung Lee, Jin Wook Yang, Hoonkee Park, Cheon Woo Moon, Dinsefa Mensur Andoshe, Jongseong Park, Chang‐Ki Moon, Tae Hyung Lee, Kyoung Soon Choi, Woo Seok Cheon, Jang‐Joo Kim, Ho Won Jang
Abstract
Abstract Although bismuth vanadate (BiVO 4 ) has been promising as photoanode material for photoelectrochemical water splitting, its charge recombination issue by short charge diffusion length has led to various studies about heterostructure photoanodes. As a hole blocking layer of BiVO 4 , titanium dioxide (TiO 2 ) has been considered unsuitable because of its relatively positive valence band edge and low electrical conductivity. Herein, a crystal facet engineering of TiO 2 nanostructures is proposed to control band structures for the hole blocking layer of BiVO 4 nanodots. We design two types of TiO 2 nanostructures, which are nanorods (NRs) and nanoflowers (NFs) with different (001) and (110) crystal facets, respectively, and fabricate BiVO 4 /TiO 2 heterostructure photoanodes. The BiVO 4 /TiO 2 NFs showed 4.8 times higher photocurrent density than the BiVO 4 /TiO 2 NRs. Transient decay time analysis and time-resolved photoluminescence reveal the enhancement is attributed to the reduced charge recombination, which is originated from the formation of type II band alignment between BiVO 4 nanodots and TiO 2 NFs. This work provides not only new insights into the interplay between crystal facets and band structures but also important steps for the design of highly efficient photoelectrodes.